Drier for sheet material



E. G. DREW 2,928,185

DRIER FOR SHEET MATERIAL March 15, 1960 Filed March 19, 1956 4Sheets-Sheet 1 4 INVENTOR. Evere H 6. Drew March 15, 1960 E. G. DREW2,923,185

DRIER FOR SHEET MATERIAL Filed March 19. 1956 4 Sheets-Sheet 2 IN VENTOR. fverci'i 6: Drew March 15, 1960 E. G. DREW 2,928,185

DRIER FOR SHEET MATERIAL Filed March 19, 1956 4 Sheets-Sheet a'IIIIIIIIIIIIIIIIII/ D 6 INVENTOR. "3 Evrezz G.Drew

March 15, 1960 Filed March 19, 1956 E. s. DREW 2,928,185

DRIER FOR SHEET MATERIAL 4 Sheets-Sheet 4 INVENTOR. .Evcrc H 6. Drew'type of drier is termed in -this type of machine,

, jets,

Un S ates P flf0 2,928,185 DRIER FOR SHEET MATERIAL Everett G. Drew,Portland, Oreg.

' Application March 19,1956, Serial No. 572,406

12 Claims. (or. 34-43 vThis invention relates-'general-ly to the dryingof a sheet of material as it lies uponand is carried by a'heated surfaceand has air impinged uponit, which air flows over the upper or exposedsurface to provide additional drying of said sheet.

This invention is particularly concerned with the formation of a sheetof paper in a paper making machine or drier having a single large drumor cylinder. This the art as a Yankee type, although it is sometimesknown as an MG machine. In a continuous, moist paper-web is plasteredagainst the peripheral surface of a heated drum or cylinder and is heldthereto by the surface tension of the moisture lying at the interface ofthe peripheral surface of the drum or cylinder and the contacted surfaceof the sheet of paper being formed and dried thereon.

In order to accelerate .the drying of the paper, the air which flowsover the distant surface of the sheet of paper, that is, the one spacedmost distantly from the heated peripheral surface of the drum,is'projected 'by'jets directed from perforated orslotted pipes which arespaced some distance from the path of the moving web.

In all such apparatus with which I am familiar, the

conduits have a fixed spacial-relaperforated or slotted tionship to theperipheral surface ofthe -drum. This is usually between three to sixinches from said surface. Experiments have been performed to vary thevelocity of said jets, the temperature thereof, and the angle. ofincidence of said jets with the opposed surface of the sheet of paper.The greatest difficulty is breaking an overlying stratum of steam orvapor which forms and collects immediately above said sheet and clingsto and moves with the upper or outer surface.

This sheathes said sheet and from the sheet as it is produced blanketsthe flow of vapor 'by the vaporization of the moisturecontent, by theheated drum upon which said sheet is plastered.

The spacial relationship has been dictated by the fact that it hasgenerally been assumedthat it is necessary to retain a substantialworking space or clearance because, requently, the sheet being formed;and dried ruptures,

and inasmuch as the sheet is formed and dried'with the sheet moving athigh lineal velocity, rupturing of the sheet while it passes through thedrier causes it to crumple and mass up in said space. This can lodge sotightly in the space that it produces disruptive pressures andscorchingaof the drum, due to the friction of the massed and crumpledpaper as it conduits and rubs against the peripheral surface ofthe drum.In that event, it is necessary to provide some type of device for pryingand pulling said massedand crumpled sheet from said space. A minimaldistance of three inches has thus been maintained for this purpose.

'Another factor which has limited the proximity of the jets orperforations to the peripheral surface of the drum, the volumes of airimpinged and directed over said sheet being dried, and the effectiveplacement of orifices or nozzles is that his necessary that the aircarrying off said vaporsmust befree to flow quickly paper being isrestrained .by the overlying .eachother.

2,928,185 rtenrea Mar. retrace ice away from said sheet and to beexhausted so as torer'nove moisture from thedrier. Efforts have beenmade to increase the number of nozzles without restricting thedischargeof said moisture laden air.

I have discovered that I am able to minimize said spacing almost twothirds by arranging jetsapproximately one inch, and in some instancesless, from the peripheral surface of the drum and to direct amultiplicity of small size jets at said optimum spacing, which providesan adequate flow of air over said sheet, and to pinpointit at closelyspaced intervals to make the carry-off of vapors more effective. I dothis by providing a multiplicity' of conduit sections arranged generallyparallel totheaxis of rotation of the drum or cylinder and providingeachconduit section with a face that is plane. Insaid plane face which isarranged in opposition'to the peripheral surface of the drtun, I providea multiplicity of, closely spaced orifices, each carrying a streamlinednozzle through which air or other drying fluid may be directed againstthe sheet of paper being dried upon said peripheral surface. I arrange aplurality of said conduits in a bank, generally two in number, and eachbank is adjustably mounted with respect to the sweep of the peripheralsurface of the drum. Said banks may be moved quickly by power means tospace said conduits, arranged in bank, from the peripheral surface, sothat access may be had in case of breakage and wadding up of a sheetofdried. I have also discovered that this retraction ofthe jets from closeproximity to the peripheral surface of'the drum, and to the sheetcarried thereby, may be done automatically by providing sensing deviceswhich produce said retraction immediately following a break or ruptureof the sheet, so as to provide a substantially greater .workingclearance. ance may be had ina matter of seconds.

For example, eight inches of clear- By providing such additionalspace,'the machine maybe stopped before damage is doneeither byproduction of wedging pressures or by scorching produced by frictionofthe wad of paper against the peripheral surface of the drum.

Other and important objects of my invention'are:

(1) To arrange nozzles inithe conduits so that the dischargeapertures ofsaid nozzles are in close proximity to the sheet of paper and are inclosely spaced pattern, so that the impingement of the air upon thesheet of paper will pierce the overlying stratum of vapor which.normally overlies the sheet and flows therewith, and thus break up saidstratum and carry it away with the drying air and thus eliminate theblanketing effect of said stratum. i 5

, (2) Producing a plurality of closely spaced "impact jets directeddownwardly upon said sheet of paper with pinpoint effect and ingenerally uniform pattern which overlies the entire area of the sheetof. paper over which air is flowed. This not only aids the drying ofasheet of paper stock, but also produces a hold-downeifect to saidsheetto augment the so-called plastering of, said sheet produced bysurface tension of themoisturecon tent upon the surface of the drum, orto supplant it if said surface tension is relaxed; v

, (3) To perform these effects without increasing the number of hot airconduits. and without conversely decreasing the areaof the passagewaysnecessary'tolaccommodate discharge of'vapor laden air from the drier.

deflected by impact with the surface of the sheet of paper and as theymushroom over the sheet. and collide with ,(i) It argues .sqaztew 'susmal 291; a the will produce high velocity directed flow, but whichnozzles in total will permithigh quantitative flow of air .pr etherdrying .fluid -without increasing the power re- ,gui merits of theblower system for flowing said air through saideonduitsand over saidsheet.

(6) To provide a patterned flow of air or other drying flnid .from saidnozzles which discharge close to said sheet, impinge ,upon it at highvelocity, and yet which iinzzles are retractable quickly to provideaccess to the ispaee adjacent said sheet-in case of breakage or otherfifl i i (7, To provide ready adjustment of said conduits and thenozzles carried thereby, so as to vary the spacing of gheischargefoutlets of said nozzles with relation to said 3. r b n d ed 8.)To proyide quick acting power means for retracting-said nozzles andautomatic sensing and operating :devi'c for quickly enlarging the spaceadjacent the pery of the drum or cylinder to prevent damage to the .drir- {These and other-features ofrmy invention, the operation ther eof,and the results that flow therefrom are e1nafterdescribedin greaterdetail with reference to accompanying drawings, in which: i

, ig. 1 isan end elevation of a machine embodying my in, cation, shownsomewhat diagrammatically with respect {in the ducts through whichdrying air flows thereto;

Fig. 2 is ,a foreshortened elevation of said machine,

' showing somewhat diagrammatically the ducts for supplying air to thehood and nozzles arranged therein;

Fig. 3 is ;an enlarged sectional detail view, showing-;sornewhatdiagrammatically .the nozzles, the jets of dryingair emittedtherefrom, and the path of flow of said air glgwnwardlyi toward a sheetof paper, mushrooming thereoyer, and the production of turbulenceinduced by im- -p act: of saidmushroomin'gjets with respect tceach otherit) :p dduce ntermediate impingement against a sheet-of paperrandtheproduction of an increased number of pressure points upon saidsheetof paper;

fig. 4 is 'a'graphicshowing of test data, illustrating the relative.amplitude of the pressure points and their locations with respect to thejets from the nozzles and the intermediate. pressure points developed bycollision of the spreadingair between the jets to produce turbulencenhddownward pressure upon the sheet of stock;

Fig. 5 .is a plan view of a plane face of a conduit secationiembodyingmy invention, showing the pattern of nozzles therein arranged in closelyspaced arrangement over the plane surface. of said conduit, whichsurface lies in close proximity to the perpheral surface of the drum;,or drying'cylinder;

Fig. 6 is a somewhat schematic view of the path of the jets of 'Iairasthey impinge against the sheet of paper, mushroom thcreover,'and impingeagainst each other to produce the intermediate pressure points betweenjets, as is-rillustrated in Fig. 4, said section being taken on the line6 -6 in Fig. 4; and Fig. 7' is adiagrammatic illustration of the sensingdevices, controls and operating mechanism by which said seaming-inplural banks may be retracted in case of breakage of the sheet 'ofstock, or otherwise.

invention is illustratedin connection with a machine which comprises astructural frame I mounted n a foundation 2. Within said frame is arotatable i or'cylindef 3, over whose peripheral surface 3a eetof.material 4 is carried and is dried.

Said drum is hollow and is supplied with steam or other heating fluidthrough a conduit 5 entering the drum s1.1b s tantially atthe axis ofrotation thereof. A hood .6 .o erlies approximately 180 degrees of saidperipheral filtfeQq as is. shown inFig. 1. Intake conduits 7-'-7aQQmmUhiCate withthe interior of said hood and carry heating air intosaid hood.' Said conduits are bo ne ssence with adjustable couplings 8to accommodate movement.

of said conduits reward"and"mayhem."ss'idursfiifss will hereinafter bedescribed The air inflow conduits 77a are more or less diagrammaticallyillustrated in Fig. 2 and supply air to the two sides 6a of said hood.

A multiplicity of longitudinal jetting conduits 10 extend between thetwo sides of the hood. To facilitate assembly of said jet conduits'withthe hood sides, I preferably arrange short .sections of conduitob uponthe interfaces of said sides 6a and they terminate in flanges 6c. Thejetting conduits are similarly flanged, and the flanges are used tojointhe jetting conduits between a pair of aligned'short sections 6b in themanner illustrated in Fig. 1. It is usual to join these'by studs-orbolts to facilitate repair and replacement. Air thus flows into saidjetting conduits from both ends thereof. This is desirablebut notessential, but I have found that this produces suflicient volumes of airfor the purpose intended and more uniform jet velocity over the entireportion of the drum and the sheet carried thereby to promote uniformdrying of the latter. It is common .to heat the air flowing in throughthe conduits 9a under most conditions, and thus 'a heater is provided(not shown) for heating the air thus applied. Conventional practices maybe observed to recirculate air and the eflicient utilization of the heatthus supplied to the drying air.

To aid in the retraction of said conduits and the jetting conduitscarried thereby, I preferably support and join said conduits in two ormore banks, as is illustrated in Fig. 2; thatis, one bank lies to oneside of the centerline of said figure and the other bank lies at theopposite side thereof. Each bank of conduits is provided with parallelguides 1111a which are fixed to the structural frame 1. Rollers 12-12aengage the guides 11 11a, respectively, and each of said rollers iscarried by its bank of conduits at each end thereof. That is to .say,one set of guides 11-11a lies at the end of a bank facing the viewer in.Fig. 2, and a companion set is arranged at the oposite end. A beam 1?:extends inter- -mediate the'ways of guide 11 and spans the entire lengthof the conduits togive structural strength and rigidity thereto. Pairsof power cylinders 1414a aligned with the guides 11 have their pistons1515a joined to said beam at its opposite ends by means of piston rods16-16a and connecting links 17--17a. The connecting links join thecylinder through' pad eyes 18.

In order that both banks of conduits will be retracted uniformly and theends of each bank will be lifted equally, I join the pistons 15-154: bya shaft 19' which is rotated by connection with the pistons 17-1711, asis illustrated in Fig. 1. Intermediate the connection of said shaft withthe cylinders, vI arrange a pairof arms 20, links v21 .andpad eyes 22.Thus, as the shaft 19 turns back and forth,.it will swing the pairs ofarms secured thereto equal radial swings and will pick up and returneach of the conduit banks equally and uniformly.

' Said banks of conduits carry the jetting conduits, as has beendescribed, and thus when the banks of conduits are arranged asillustrated in Fig. 1, it is necessary that the conduits occupy. acorrect spacial relationship with regard to the peripheral surface 3a ofthe rotatable drum.

This is accomplished by providing an adjusting screw 1duitsj that is,there are four adjusting screws, two of which engage the beam on theleft hand bank of conduits, one' at each end, "anda similar arrangementis provided {for the right hand conduits,

lies viewed in Fig. 1 ,th'e'drum' or cylinder 3--rotates irracounterclockwise direction, as is indicated by arrows. The sheet ofmaterial 4 overlies the peripheral surface 3 a,thereof,and thus thepaper enters at the lower right handfside of said figure andis-discharged at the lower left hand side. Supported by the guide 11a atsaid right hand side which forms a part of the fixed framework of themachine is a feeler or sensing device 25. It has a riding arm 25a whichrests lightly upon the sheet of material and which is carriedalong bythe drum. If said sheet of material breaks, the feeler or sensing deviceis tripped to cause the power cylinders to lift the jetting conduitsmore or less radially from the drum a distance of about eight inches, soas to provide a large working clearancebetweenthe peripheral surface ofthe drum andthe most closely adjacent surfaces of the jetting conduits10. I have illustrated this somewhat diagrammatically in Fig. 7.1 1 1 eIt is to be understood that the feeler or sensing .de-

, vice 25 and itsriding arm 25a is only exemplary'of any type of sensingdevice. The ultimate end which I have in mind is to provide a devicewhich will sense a break or rupture in the sheet of material 4. This maybe mechanical-electrical, as is illustrated and described, or it mightbe photoelectric in which the presence of the uninterrupted sheet ofmaterial intercepts the beam, and when said. sheet is broken, themaintenance of the beam will actuate the means for moving the jettingconduits 10 and their nozzles away from the peripheral surface of thedrum in order to provide the desired clearance. The feeler or sensingdevice also might bear upon a span of paper'as it is discharged from theroller rather than to sense it at the point of entry of the moist stockunder the hood. The advantage of the location selected and illustrated,however, is that it is at this point that any massing or crumpling ofpaper would be initiated, in all probabilities, and as the paper,following a break, would tend to mass up at this point and would producepressure which'would be sensed by and transmitted to the operatingmechanism, which would respond to the emergency condition thus createdand the parts would be rapidly separated before damage occurred.

. As is shown in Fig. 7, the feeler or sensing device actuates a switch26 in'thecontrol circuit 27. The actuation of said switch operates ahydraulicjvalve 28 by means of a solenoid 29 to supply fluid through theconduit system 30 to all four powercylinders 14-14a. The actuation; ofsaid, cylinders causes the bank of conduits to be-quickly lifted, thatis, retracted from the drum, as-hasbeen described. Said jetting conduitsare quite massive and will return by gravity to the position they occupyin Fig. 1 when the sensing device 25 is returned into bearingrelationship withthe sheet of material. I preferably provide a maincontrol switch 31 in the electrical control circuit 27. Said maincontrol switch or other control element can make the operation andretraction of said parts manual rather than automatic and also provide asafety factor for holding the parts spaced apart, if such is desirable.Referring now to Figs. 3 and 4: v

It is desirable thatthe face wall 32 of each of the conduits 10 ffOllOWgenerally the sweep of the peripheral surface 3a of the rotatable drum.Thus, said conduits 10 are arranged generally in acircular coursesurrounding and facing said peripheral surface, as is shown in Fig. 1..Said conduits preferably are of rectangular section, as is shown insaid figure, and in a typical installation said conduits areapproximately twelve inches deep: They extend-the full width of, thepaper, as is indicated in Fig.2.

Machines generally accommodate sheets of paper stock from about eightfeet wide to about twenty feet wide, and thus each of the conduits 10 isof corresponding length.

.I-have-found-that I getthebest results byproviding nozzles 33, eachhaving a discharge aperturepfqaboutoneover the surface of the sheet ofpaper.

each nozzle and they descend. quite sharply.

quarter inch, the nozzles being three-quarter's inch long. Theypreferably are of the reentrant type, that is, they lie inwardly of theface wall 32 "and terminate the exterior face of wall 32. I have foundthat nozzles of streamlined contour operate most efliciently. Inalludrying machines with which I am familiar, in which air is directedby jets over a surface of a sheet to be dried, the apertures ordischarge nozzles have either. been perforations through the wall of theconduit, or standrad mouth pieces, or else they have been reentrant tubedischarge outlets or examples of Bordas mouthpiece. A Borda mouthpieceis one in which the reentrant'tube is of cylindrical form and is half aslong as the diameter of the orifice. The reentrant tubes haveextendedinwardly from the face fo the conduit a distance two or three times thediameter ofv the orifice. With a Borda mouthpiece, high velocities areattainable'on the order of an empirical scale of about 99', but thequantitative flowv is on the order of 54 onra similar scale. The reasonis that the Borda mouthpiece contracts the jet as it flows over therelatively sharp entrance edge, which substantially restricts the volumeto produce the higher velocity. On the other hand, a reentrant tube two.or 'three timesas long as the diameterof the orifice cuts down thevelocity to about 72 on 'said scale and has a quantitave flow of about72. i

I have discovered by measurement and test that with a bell-shapedreentrant tube of streamlinedcontour such as is illustrated in Fig. 3,the velocity is maintained at about 96 on said scale and thequantitative flow is about 96. Thus, jets of high velocity are emittedand there is little restriction to flow through the orifice. The emittedjet also seems to hold its cylindrical pattern or cross sec; tion betterthan one emitted by either of the other two orifices. That is to say,the angle of divergence seems slight, and thus the entire jet of air isdirected throughspread out and mushroom and sweep over the surface ofsaid paper. This is graphically shown'in Fig. 4.

The peaks x underlie the axis of the jet emitted from Lying intermediatesaid peaks are ones of lower amplitude y which develop when nozzlesone-quarter inch in discharge aperture size, three-quarters inch long,belled as is shown, and

spaced apart one and a quarter inches apart are arranged approximatelyone inch away from the upper surface of a sheet of paper to be dried. Iam unable to explain definitely why these intermediate peaks occur, butthey do. It seems logical to suppose, as is illustrated diagrammaticallyin Fig. 3, that they are produced by the impinging of adjacentmushrooming jets as the jets flow They likewise rise and fall sharply.In said test, air velocities were maintained slightly above 13,000 feetper minute. When vthe spacing is increased above one inch, saidintermediate peaks rapidly diminish and flatten out, and this islikewise true when a spacing of the nozzle to the paper is less thanone-half inch. The amplitude of the major peaks xincreases substantiallyat the smaller spacing, but the intermediate peaks do not occur. This iscritical between an orifice spacingfrom the sheet of from one-half inchto two inches and with jets having outlet diameters of fromthree-sixteenths inch to one-half inch -at -the attained velocities. Ibelieve this to be an important factor in the efliclent drying of paperbecause the production of these numerous pressure points or applicationsof impact air to the sheet produces more rapid drying of said sheet.

My experience, further, has been that when an optimum relationship suchas described is maintained, there is a substantially less tendency torupture the sheet of paper being dried than previously. Certainly, thepressure a generated by said numerous impact points would tend to holdthe sheet to the surface of the drum -more securely than li -they werenot of the-attained amplitude and pattern. Nomial-l-y, .the,;paper I1's"plastered* to the peripheral surface of :the .drum :by the surfacetension ,of the water content ofthe sheet where :itlies as ,-a filmbetween the opposed .surfaces of the sheet and the drum. If the sheetdries .too rapidly at "the interface and said water film is .vaporizedunevenly, the uniform surface tension is relaxed .andthe paper vtends toblow Off the peripheral surface f .the drum.

' The presence of the plurality of pressure points, saythree-.fourthsinch apartover the entire area, would tend to :providesome force greater than a generally elevated air pressure'extending overthe sheet, to preventdislodgment .of .the sheet from the peripheralsurface of the drum. In anyevent, inmy experience, the rupturingof thesheet and the consequent stopping of the machine has beenmateriallydiminished when .my invention has been .used, and my observation of thefactors involved :leads .me' to the conclusion that this is produced bythe uniform pattern of closely spaced pressure points over the entiresheet of. ;paper :being dried .under' the air hood.

:Infig. 6, Ihave shown somewhat schematically the flow linesproducedwhen-a jet strikes the surfaceof the paper, which is arrangedsubstantially normal to the jet, as isillustrated. The outward -floworsplatter over the sheet of paper .quickly strikes the opposed outwardflow from adjacent jets and the splatter produced by collision .withadjacent jets. The impact of two of said jets moving .in :oppositedirections and of approximately equal .velocities wouldproduce a.downwardfiow, or at least a downward component ,of force, against thesurface of the paper. This is evidenced by graphs developed bynumerfoustests. In other .words, said'midpoints y shown on the graphzinFig. .4.do occur routinely, and it is for the reason, I believe, that I havejust described.

Said peaks are developed by impact of the jets upon asurface oftheisheet of stock being dried. They are of relatively high amplitudeand tend topierce the stratum of .vapor which is possibly a thousandthsor two-thousandths of an inch in thickness. Said stratum is developed bythe heat of the drum in the paper stock, and

tends .to blanket the stock and to inhibit the outward flow of followingvaporous moisture from the stock. By piercing this blanket in numerousplaces and sweeping it ina turbulent flow from proximity with a sheet ofstock, I eliminate said blanketing influence and ac tolerate the rate atwhich vapor is absorbed by the air and carried out of the drier and,correspondingly, increase the :rate at which the stock is dried. As'hasbeen point out, the sum of the number of peaks x and y is double that ofthe nozzles in each row and is augmented between successive'rows. Thus,with the-same number of nozzles or orifices, the pressure points arepatterned more closely and are increased substantially 'in'numberwithout the addition of other nozzles, which was heretofore considerednecessary.

The provisionof bell-shaped reentrant tubes, or socalled streamlinedcontour nozzles, permits the orifices of the several nozzles to bediminished in diameter and the number of nozzles to be increased withoutcorrespondingly decreasing the volume of flow of air through saidnozzles. This permits me to use nozzles of from three-sixteenths inch toapproximately one-half inch diameter rather'than from five-eighths inchto one inch in diameteiy -as was previously done. I believe this to be amatter of consequence because resistance to fiow through an aperture issubstantially inversely in proportiontoithe square of area of theaperture. Thus, when apertures one-half inch in diameter are used ratherthan those of one inch in diameter, the area of said apertures isdiminished three quarters. When air-is forced through an apertureone-quarter inch in diam- 'cter, ithas a'cross'sectional'area of onlyone-sixteenth that 'ofan inch diameter aperture. The volume of airwhichnecessarily must be flowed through driers 'of this %typeand'capacity=require blowers of largesize to be erupts io csa s zb manss t am 2. ili-i I91 Q0Ji-P- It i thusss snt a tha -.theai W rpugsa dprtu e at hi h e oc ty and minim m es ri t cn p i u a y a a as yq me ricflow is concerned. Said bell-shaped reentrant tubes or streamlinedorifices perform this function well and produce @jetshaving thedesirable characteristics vto which I have hereinabove referred. 1

I .have not illustrated the encompassing hoodtoriroom into which thedischarged moisture laden airflows from the hood becausethis .is more orless conventional-andis well ;known in the art. In any event, this airis-sometimes wholly wasted to the atmosphere, sometimes-whollyrecirculated, and at other times it isintermixed with proportionatemake-up air and returned to the machine '1. A paper-making machine fordrying a continuous sheet of material directed .over the peripheralsurface of a rotatable drum which is maintained at a temperaturesubstantially above atmospheric, comprising a hollow hood memberpartially encircling the :periphery of said drum, means for directingair under pressure ;;to the .interior .of said hood, a series oflongitudinally disposed conduits arranged in a circular sweep generallyconcentric with the'peripheral surface of said'drum, and streamlinedborebell-shaped nozzles arrangedin each of said conduits and havingdischarge outlets directed toward the peripheral surface of said drum,where the nozzle:diameter is less than approximately one-half inch, thenozzles are spaced less than approximately two and .one-half inchesapart, and said nozzles terminate less than approximately two inchesfrom the drum surface.

2. A paper-making machine for drying a continuous sheet of materialdirected over the peripheral surface of a rotatable drum which ismaintained at a temperature substantially above atmospheric, comprisinga hollow hood member partially encircling the periphery of said drum,means for directing air under pressure to -the.interior of said hood, aseries of longitudinally disposed conduits each having a wall arrangedin a circular sweep generally concentric with the peripheral surface ofsaid drum, and reentrant-type streamlined-bore bell-shaped nozzlesarranged in each of said conduits and having discharge-outletsterminating at the exterior face of said wall and directed toward theperipheral surface of said drum, where the nozzle diameter is less thanapproximately one-half inch, the nozzles are spaced less thanapproximately two and one-half inches apart, and :said

nozzles terminate less than approximately two inches' of a rotatabledrum which is maintained at a temperature substantially aboveatmospheric, comprising a hollow hood member partially encircling theperiphery of said drum, means for directing air under pressure to theinterior of said hood, a series of longitudinally disposed conduits eachhaving a wall arranged in acircular sweep generally concentric with theperipheral surface of said drum, each of said conduits having agenerally plane exterior face carrying a plurality of equidistant rowsof nozzles including a plurality of nozzles spaced a predetermineddistance apart in each row and terminating at-the exterior face of saidwall, where the nozzles are less than one inch in diameter, are spacedapart in each row less than approximately two inches and terminate lessthan approximately two inches from the drum-surface.

4. Claim 3 modified inthat said nozzles-are less than ones-halfinch indiameter-and arespaced apart from adjacent nozz es a distance lessthantwoinchesf aud morc thanone-half inch.

5. Claim 3 modified in that said nozzles are less than one-half inch indiameter and are spaced apart from adjacent nozzles a distance less thantwo inches, and that the discharge outlets of said nozzles are spacedfrom the peripheral surface of said drum a distance less than twoinches, and more than one-half inch.

6. Claim 3 modified in that said nozzles have discharge outletsapproximately one-quarter inch in diameter, are spaced approximately oneand one-quarter inches from adjacent nozzles over the generally planeface of each conduit, and are spaced from the peripheral surface of webof paper directed over the peripheral surface of a rotatable drum, whichdrum is maintained at a temperature substantially above atmospheric,comprising a hollow hood member comprising plural units, each unitoccupying about 90 of the circumference of said drum, individual meansfor directing air under pressure to each of said hood units, a conduitcarried by each of said hood units into which said means discharges,each conduit having a wall arranged upon a circular sweep generallyconcentric with and adjacent the peripheral surface of said drum, pluralguideways for each of said units delining a path of travel toward andfrom said drum, which path is substantially radial to the circular sweepof the unit being guided, said pathways thereby diverging with respectto each other, sensing means responsive to web breakage, means activatedby said sensing means upon web breakage for moving said plural unitssimultaneously toward and from said rotatable drum, each along its arotatable drum which'is maintained at a temperature.

substantially above atmospheric, comprising a hollow hood member aboveand partially encircling the periphery of said drum, said hoodcomprising plural sections mounted for movement along divergingsubstantially radial separate paths, means for directing air underpressure to the interior of said hood, a series of longitudinallydisposed conduits arranged in a circular sweep generally concentric withthe peripheral surface of said drum,

nozzles arranged in each of said conduits and having dis charge outletsdirected toward the peripheral surface of said drum, sensing meansresponsive to web breakage and operating means activated by said sensingmeans upon web breakage to lift said nozzles from the peripheral surfaceof said drum as units to provide access to a space of substantiallyuniform breadth between the conduits and the peripheral surface of saiddrurn.

9. Claim 8 modified in that said pressure-sensitive operating means arepower actuated.

10. A paper making machine for drying a continuous web of paper directedover the peripheral surface of a rotatable drum, which drum ismaintained at a temperature substantially above atmospheric, comprisinga hollow hood member comprising plural units, each unit occupying about90 of the circumference of said drum, individual means for directing airunder pressure to each of said hood units, a conduit carried by each ofsaid hood units into which said means discharges, each conduit having awall arranged upon a circular sweep generally concentric with andadjacent the peripheral surface of said drum, plural guideways for eachof said units defining a path of travel toward and from said drum, whichpath is substantially radial to the circular sweep of the unit beingguided, said pathways thereby diverging with respect to each other,sensing means responsive to web breakage, and means activated by saidsensing means upon web breakage for moving said plural unitssimultaneously toward and from said rotatable drum, each along itsrespective path.

11. A paper making machine for drying a continuous respective path, saidmeans moving each of said head units over a predetermined range ofmovement along its path between preselected limits.

12. A paper making machine for drying a continuous web of paper directedover the peripheral surface of a rotatable drum, which drum ismaintained at a temperature substantially above atmospheric, comprisinga hollow hood member comprising plural units, each unit occupying aboutof the circumference of said drum, individual means for directing airunder pressure to each of said hood units, a conduit carried by each ofsaid hood units into which said means discharges, each con- I duithaving a wall arranged upon a circular sweep generally concentric withand adjacent the peripheral surface of said drum, plural guideways foreach of said units defining a path of travel toward and from said drum,which path is substantially radial to the circular sweep of the unitbeing guided, said pathways thereby diverging with respect to eachother, sensing means responsive to web breakage, and means activated bysaid sensing means upon web breakage for moving said plural unitssimultaneously toward and from said rotatable drum, each along itsrespective path, each conduit wall of a hood unit having nozzlesterminating in a common sweep at the surface of said wall adjacent saiddrum, the means moving said head units a'substantially uniform distancealong said path,.thereby to provide access to a I space of substantiallyuniform breadth between all of the conduit walls and the peripheralsurface of said drum.

Germany Sept. 11, 1941

